The following essay is drawn from old pranayama classes that I held in Holland in the eighties
Sit in Padmasana or Siddhasana
Bring the head down in Jalandhara Bandha. Close the eyes and follow the movement internally.
The teacher can only say things, show things, but you have to pull the teaching into your body, and do it. No teacher can do it for you. Whatever I say, look inside your body. Take care and responsibility for what happens inside your own personal universe, your body and mind. Be really inside your body and take care of it, because nobody else can or will do it for you.
Watch the breathing, the normal breathing. Find out in your own body where it goes smooth and easy and where it is not so easy. Certain parts of the body are more stiff, certain parts are more supple. Look inside the cavity of the chest and find out for yourself.
The chest is like a balloon. When you blow air into the balloon, if it is a normal balloon and not one of those knotted ones, the air will go simultaneously and equally in all directions. Forwards, backwards, down and up. Sideways.
Find out for yourself if this is the case. Maybe one part of the chest is more closed, does not receive so much air, maybe because there is a dis-level in the shoulders, or the shoulder blades, or the spine is turning.
When the air does not move easily in a certain part, find out what the skeletal structure is doing, the shoulder blades. Usually when one part of the chest does not receive as well as the other one is because that shoulder blade is more round.
For the chest to be open the shoulder blades have to be flat between the skin and the rib cage. If they are round, which means that the point of the shoulder blade points backwards instead of downwards, then of course that part of the chest will be more closed. As the arm will go more forward, the shoulder will go forward and so the upper ribs cannot open so well.
Also see where the air passes through the throat. Normally it passes quite high through the throat, right underneath the jaw. That means that the movement of the breathing is confined to the chest, which of course anatomically speaking is correct, as the chest contains the lungs. This type of breathing is called Ujjayi pranayama, a classical breathing.
But that is only an anatomical concept. The more holistic concept would be that the whole body participates in the breathing. Which is also true. Both these concepts are true on their own way.
Because we want to make a more holistic approach and turn the whole body into one total unit of movement and information and not partially here and partially there we need to bypass the idea that the breathing takes place in the lungs and we need to involve the whole body.
To do that we need to shift the breathing from the upper throat into the lower one, and that is exactly what nature has provided. The diaphragm is the wall which divides the chest from the abdomen. Which means the lungs, the breathing apparatus from the digestive apparatus, from the food container.
The diaphragm being a wall between those two areas is also like a sponge which absorbs a lot of tension. A lot of negative tension goes into the area of the diaphragm. The liver, the stomach, the diaphragm, that is where negative energy is stored.
Nature has provided the means of releasing that negative energy. That is through an opening way down in the throat. Also quite back in the throat, not in the front, but in the back of the throat.
It is the opening which we use every day when we either yawn or when we sigh. It is called a sigh of relieve, because that is exactly what it is.
Breathing or yawning through that opening takes you straight down into the diaphragm, into the negative center, and it releases it, that is why it is called a sigh of relief, it releases it, and therefore the negative energy can flow out of the body.
Now you pretend that you want to yawn, you almost initiate a yawn, but then you change your mind and instead of yawning you inhale through that opening. Which is way down in the throat and back, close to the spinal column. You will see if you do that that in the first place that opening down immediately has an widening effect on the chest.
It also has an immediate negating effect on the diaphragm as a wall dividing the chest from the abdomen. The chest and the abdomen become one huge space, a huge room, not a room divided by a wall. This is what the Mula Bandha breathing is based on. Eliminating that wall through breathing in the lower throat means that the movement can go way down into the lower abdomen and then the inhalation upward movement starts way down in the pelvis.
As you yawn without yawning and inhale through that area you can feel how the chest widens, and then keeping the kidney region back and the sacrum firm see how immediately also the lumbar region and even the sacrum region widens.
Then, when you inhale, it starts from right there. The lower abdomen moves back towards the sacrum, the sacrum does not yield and therefore the movement will then turn upwards again and flow up along the lumbar spine.
Keeping the kidney region back it then widens the kidney region, and still flowing upwards along the spinal column, it reaches the shoulder blades, widens the shoulder blade region, and then it goes into the ears, let us say, and from the ears it flows forwards and down through the jaw into the Jalandhara bandha out in the exhalation.
As the spinal column flows upwards of course the sternum moves upwards, but keeping the xyphoid process pointing in the direction of the pubis, not forward. You can feel that the whole upper chest, the manubrium, will open and widen together with the shoulder blades.
As it widens the jaw comes down to meet the upcoming sternum and where the jaw connects with the neck, there is a widening. The upper chest and the upper neck, just between the jaw and the back of the skull, widen simultaneously (the hood of the cobra).
The base of this whole edifice is the pelvis, the pelvic bones should be immovable, the sacrum should be firm, the buttock bones rooting down, and then the spine can elongate upwards out of this stable pelvis up till the top of the neck, after which the jaw can detach itself from the neck and come forward and down.